A glider's best friend

Ian Morton’s photograph of strange-looking poles popping up beside the Hume Highway near the NSW/ Victoria border (‘‘Odd poles’’, July 14) prompted a number of different explanations, some more plausible than others.

Several readers, such as David Roach, of Braddon, suggested that as the poles started to appear around the same time as the duplications of the highway that they are part of a temporary measure to move electricity around the building site.

Backing up Roach’s theory was John of Tuggeranong who ‘‘ vaguely recalls seeing some of them with power cables attached and wondered if they were to keep temporary power cables a safe height above construction vehicles’’.

Meanwhile, one reader, who requested anonymity, claimed the ‘‘erratic positioning of the poles with some in clumps and others standing alone’’ might be part of ‘‘some sort of scientific attempt to communicate with alien life forms’’.

However, all kudos must go to David Kerr, of Stirling, who offered the most logical explanation: ‘‘The poles are designed to reduce the potential impacts to the threatened squirrel gliders (Petaurus norfolcensis), helping them to safely cross the highway following its widening through duplication.’’

A missive fired off by the NSW Government Roads and Maritime Services confirmed Kerr’s theory. It says, ‘‘the gliders jump from tree to tree in search of food, shelter and mates. When trees are cleared for roadwork it can lead to gaps too large for the gliders to cross by gliding. The poles help to fill the gaps in the short term.’’

As to the ‘‘erratic positioning of the poles’’, according to the RMS, ‘‘a single pole is used to fill small gaps in the treelines and groups of poles are used to cover larger gaps or to suspend rope crossings [which are designed to assist arboreal marsupials to cross the road]’’.

The 46 poles vary in height to cater for the glide angle and distance, but most are about 20 metres high. Each glider pole is different for various reasons such as length, location and fixtures and as a result they aren’t cheap, costing about $17,000 each.

Are the poles working?

Dr Rodney van der Ree, deputy director of the Australian Research Centre for Urban Ecology (a division of Royal Botanic Gardens Victoria) says monitoring indicates that both the glider poles and rope bridges are used.

‘‘If we install these structures in the right places, and there are populations of arboreal marsupials nearby, they will use them,’’ he says, adding, ‘‘research by PhD candidate, Ms Kylie Soanes indicates that crossing rates by squirrel gliders at poles in Victoria average about 0.4 crossings per night’’.

Despite all this effort, the poles are only temporary. It is hoped that strategically planted vegetation will replace the poles in the longer term.

Who knows, maybe then they can be used to communicate with aliens!

Have you seen any wildlife using the ropes or poles? If so please let me know.